I looked at my detriot diesel service manuel and it says 1% max. So at least two sources I have found say 1%. detroits uses a luberfiner bypass filter for a lot of their engines. By the way this is all the old 2 cycle engines. I have not yet worked on the newer 4 cycle.

I have been using the Amsoil bypass for my 240, and my Dodge. Luberfiners on the larger engines.

Even if there is enough clearance for the dirt particles, they are not always suspended in the middle of the oil stream. Those at the edges are going to cause wear. Think like lapping compound. I know this is not the scientific answer you may be looking for, but hope it helps.

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1977 240D turbo